A fuel cell has a general structure composed of an anode, a cathode, and a polymer electrolyte membrane. The anode includes a catalyst layer for promoting fuel oxidation, and the cathode includes a catalyst layer for promoting reduction of an oxidizing agent. At the anode, hydrogen ions and electrons are generated due to fuel oxidation. The hydrogen ions are delivered to the cathode through the electrolyte membrane, and the electrons are delivered to an external circuit through a conducting wire. At the cathode, the hydrogen ions delivered through the electrolyte membrane, electrons delivered from the external circuit through the conducting wire and oxygen are combined, thereby generating water. At this time, electron transfer from the anode to the cathode via the external circuit is electric power. The cathode and anode of the fuel cell include catalysts for promoting electrochemical oxidation of fuel and electrochemical reduction of oxygen, respectively.
Performance of a fuel cell is considerably influenced by catalyst performance of a cathode and anode. As a catalyst material suitable for an electrode, noble metals such as platinum have been widely used. Especially, a Pt/C catalyst in which platinum particles are impregnated on a carbon support having a high specific surface area and a good electrical conductivity has been representatively used. However, because platinum is very expensive, there is a need to maximize catalyst performance by reducing the amount of platinum used in the particle impregnation and optimizing impregnation-related factors so as to achieve successful impregnation with only a relatively small amount of platinum.
For this, an electrode catalyst in which alloy particles of platinum (Pt) has been recently developed, and other transition metals such as nickel (Ni), paladium (Pd), rhodium (Rh), titanium (Ti), zirconium (Zr) and the like are impregnated on a carbon-based support. However, the carbon-based support has problems in that it is unstable under electrochemical conditions of an electrode and easily oxidized, leading to a falling-off in long term stability. In order to solve these problems, there have been several studies to employ a transition metal oxide being stable under an acidic condition as a support, but the transition metal oxide exhibits relatively low electrical conductivity, and thus, it is difficult to sufficiently ensure the performance of a fuel cell.
Meanwhile, titanium suboxide (TSO) has been developed as a transition metal oxide. According to a conventional method, titanium suboxide is prepared as a micron-scale particle through a high temperature reaction at 1200° C., which makes it difficult to use titanium suboxide as a catalyst support.
The present disclosure endeavors to overcome the prior art problems as set forth above by describing a method for synthesizing nano-scale titanium suboxide at a temperature ranging from 600° C. to 900° C. by applying Co2+ ions as a catalyst for decreasing a temperature required for heat treatment of nano-scale titanium dioxide under reducing atmosphere (under hydrogen, nitrogen or methane gas). The titanium suboxide nanoparticle according to the method of the present disclosure has a high conductivity enough to improve long term stability of a catalyst electrode for a fuel cell. When a metal catalyst is manufactured by using the titanium suboxide nanoparticle as a support, the metal catalyst can significantly enhance efficiency and durability of a fuel cell.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the disclosure and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.